1. Field of Inventions
The present inventions relate generally to fuel cells and, more specifically, to fuel cell bipolar plates.
2. Description of the Related Art
A fuel cell converts fuel and oxidant (collectively "reactants") into electricity and a reaction product. Many fuel cells employ hydrogen as the fuel and oxygen as the oxidant. Here, the reaction product is water. One such fuel cell is the proton exchange membrane (PEM) fuel cell. Each individual cell in a PEM fuel cell includes an anode and a cathode separated by a thin, ionically conducting membrane, which together are often referred to as a membrane electrode assembly (MEA). The anode and cathode, on opposing faces of the tonically conducting membrane, are comprised of a thin catalyst containing film and a gas diffusion layer. Hydrogen is supplied to the anode and oxygen supplied to the cathode. The gas diffusion layer insures that hydrogen is effectively transported to the anode catalyst and that oxygen is effectively transported to the cathode catalyst. The hydrogen is electrochemically oxidized at the anode catalyst, thereby producing protons that migrate across the conducting membrane and react with the oxygen at the cathode catalyst to produce water. The individual MEAs are stacked in electrical series with impermeable electrically conductive bipolar plates therebetween that conduct current between the anode of one MEA and the cathode of the adjacent MEA. Conventional bipolar plates are flat plates that have one or more channels formed on one side for transporting fuel over one MEA and one or more channels formed on the other side for transporting oxidant over another MEA. The oxidant channels may or may not be aligned with the fuel channels.
Fuel cells are considered an attractive energy source for a variety of reasons. As compared to batteries, fuel cells are advantageous in that they can maintain a specific power output as long as fuel is continuously supplied and are not hampered by a charge/discharge cycle. Fuel cells are also relatively small and lightweight and produce virtually no environmental emissions. PEM fuel cells are particularly advantageous because they have relatively low operating temperatures and employ a non-liquid, non-corrosive electrolyte.
Despite these advantages, the inventors herein have determined that conventional fuel cells are susceptible to improvement. For example, the inventors herein have determined that it would be desirable to reduce the size and weight of conventional fuel cells. The inventors herein have further determined that such reductions in fuel cell size and weight can be realized through improvements in the design of the bipolar plates that separate adjacent MEAs.